Equilibrium band diagrams of HSCs based on p-a-Si:H related to the cross-sectional structures in b and c . E C , E V and E F denote conduction band energy, valence band energy and Fermi level, respectively. Insets: enlarged view of the black wire frames; there, Δ E equals the difference between E F and E V at the i-a-Si:H–n-Si interface. The collection path of holes across the heterojunction is depicted as a more complicated curve (red arrows) for p-a-Si:H to illustrate a more challenging transport mechanism at the relative interfaces, with respect to the p-nc-Si:H counterpart. Current is generated once the holes meet and recombine with the electrons (along blue arrows) at the interface of the TCO–hole transport layer.
